I think you can (I can in Paint shop Pro) but I would reconsider because if the background is going light blue to dark blue and the text is going the other way, somewhere in the middle the colors will be the same:

The second one I made using a screen cap blown up to god knows how large (I stopped keeping track at 800%).

Up close it looks alright, nowhere near as stunning as it would be if it were an original scan.

Its a piece of conceptual artwork, with the 20K logo taken from a lobby card, and the tagline and actors name was a layout I took from another poster (I would have put their heads also like the original, but knowing everyone's fondness of floating heads I opted not to).

2nd cover is great.
From my monitor, I can't tell if the background
is black or dark blue / grey?
Would you consider moving just off of black into
the dark blue / grey on the diver's suites?
A color a little darker than your first cover.
I loved how you were trying to simulate the
dark underwater effect.

2 & 4 are very nice!
The texts on the back looks easier to read.
The red text on the front does look hard to read.
Maybe a foam green or yellow green????
Or maybe a silver like the moon's reflection
on the night's water surface???